Presso la sezione di Roma INFN è attivo da molti anni un gruppo che si dedica allo sviluppo 

di rivelatori sempre più sensibili di onde gravitazionali (non ancora osservate direttamente)

e che oggi fa parte della collaborazione Virgo.

Misura della conducibilità termica (I) e del fattore di qualità meccanico (II)di fibre di zaffiro (Al2O3)

ELiTES:ET‐LCGT Interferometric Telescopes Exchange of ScientistsWork‐Package 1 and 2: cryogenics and suspensions

In construction !!! The future ???

KAGRAL 3 km

Einstein TelescopeTRI 10 km

BOTH UNDERGROUND, CRYOGENICS 

Majorana, Puppo,Rapagnani, RicciG23, Marconi

Proposte @G23 AA 2012‐13R&D

Cryogenic facilities for mechanical quality factor and thermal conductivity at the INFN‐Rome laboratory (University of Rome “La Sapienza”)

E. Majorana

Cryogen cryostats (3)

Cryogen‐free cryostats (2),the most used in last years

2.Sapphire fiber at Rome

2.Cryogenic payload

Vibration measurement of the KAGRA radiation shield

1.IntroductionThe Large-scale Cryogenic Gravitational Wave Telescope named KAGRA is under construction in the Kamioka mine in Japan. The main interferometer mirrors will be cooled down to 20K in order to decrease the thermal noise. For cooling, each of these mirrors will be surrounded by a double-stage radiation shield to prevent propagation of 300K radiation and will be connected to two cryocoolers through heat links. The shield vibration can couple into the detector signal via the heat links and scattered light. In order to investigate the impact on the KAGRA sensitivity, we measured the radiation shield vibration while operating the cryocoolers. Then we estimated the influence on the sensitivity of KAGRA. Here, we report the measurement result for the KAGRA cryogenic radiation shield vibration and analysis result.

Impact of the radiation shield vibration on the interferometer noise:

1.The vibration of the radiation shield may excite an oscillation of the test mass through the heat links.

2.The scattered laser light is partially reflected by the baffle (connected with shield) and might find its way back into the main laser beam, contaminating the output of detector.

chendan@icrr.u-tokyo.ac.jp

The main sources of the shield vibration:1. Seismic motion2. Cryocoolers

Cryogenic payload: cooled suspension system and mirror

Pulse tube0.9 W at 4K (2nd)36 W at 50K (1st)

Heat links

T=20K

8K80K

Laser

Radiat ion shield

Cooling bar

Cryo cooler

Cryo cooler

Testmass

Baffle

Measure the vibration of the radiation shield at low temperature, and estimate the influence on the sensitivity of KAGRA.(Measurement @Toshiba Keihin Product Operations, Yokohama-city).

3.Measurement in ToshibaWe used an accelerometer developed in Rome Univ. for vertical direction and a Michelson interferometer as an accelerometer developed in ICRR for horizontal direction.

Dan Chen, K. Yamamoto, Ettore MajoranaB, Luca NaticchioniB, T. SuzukiA, N. KimuraA, Andrea ConteB, S. KoikeA,T. KumeA, C. Tokoku, Y. Sakakibara, Alexander Khalaidovski, S. Kawamura and KAGRA Collaboration

ICRR The University of Tokyo, KEKA, INFNB

ET meeting 22nd-23rd Oct. 2013 @ Hannover

INFN acc. ICRR acc.

Inside the shield

We used a commercial accelerometer(RION) to measure the vibration outside the cryostat. We measured the vibration at low temperature with cryocooler ON/OFF.

RION

Coolers OFF

Consistentwith RION

Increase

10-11

10-10

10-9

10-8

10-7

10-6

1 10 100

Vibration [m/rtHz]

f [Hz]

seiswrion0819100hz09.eps

T=10.1K

Inside the cryostatOutside the cryostat

Measurement with coolers ON/OFF (horizontal)

10-11

10-10

10-9

10-8

10-7

10-6

10-5

1 10 100

Vibration[m/rtHz]

f [Hz]

ptonoff092501.eps

PT ONPT OFF

There are many peaks originating from the coolers.

Assume the same peak level at Kamioka as Yokohama

Coincidence measurement with RION (horizontal)

The estimated vibration of the radiation shield at Kamioka has peaks from cryocoolers.

10-13

10-12

10-11

10-10

10-9

10-8

10-7

1 10 100

Vibration [m/rtHz]

f [Hz]

shieldpeakatkamioka08070203.eps (T=10K)

shield at kamioka PT ONKamioka

10-3410-3210-3010-2810-2610-2410-2210-2010-1810-1610-14

1 10 100

Strain [1/rtHz]

f [Hz]

KAGRA design sensitivityNoise from radiation shild

Horizontal

component

4.Measurement result and analysis

Calculate the ratio to estimate the floor level at Kamioka.

10-3010-2810-2610-2410-2210-2010-1810-1610-14

1 10 100

Strain [1/rtHz]

f [Hz]

luca0819strain100hz.eps

designNoise from radiation shild

Verticalcomponent

We estimated the influence on the sensitivity of KAGRA using a code made by T. Sekiguchi.The scattered light effect is not considered.

We inputed our estimated vibration to the attachment points between heat links and shield.

The noise from the horizontal vibration component is significantly lower than the requirement. But the noise from the vertical component is higher than the design sensitivity around 20Hz.

We have to take care of vertical vibration when we design the cryo-payload.

Measurement of sapphire Q for KAGRA mirror suspension

Sapphire fiber

1.PurposeWe will use sapphire fibers (φ 1.6 mm) to suspend cooled sapphire mirrors(20K).

High thermal conductivity → lower cooling timeHigh Q value → lower thermal noise

RequirementsThermal conductivity: 5000 W/m/KQ value: 5x106 etc...

In Rome we tested two samples with good thermal conductivity.

Fiber 1: 5000 W/m/K @20KFiber 2: 9000 W/m/K @20K

Our purpose is measuring the Q value of these fibers @ 20K

Fiber 1• 5000 W/m/K @20K• Monolithic

• 9000 W/m/K @20K• Non-monolithic• Brazed through alumina

• HEM quality• Thermopolishing

Fiber 2

3.Measurement setup

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0 5000 10000 15000 20000 25000 30000 35000 4000045000

signal[V]

time[s]

deti1015005at16p41kr.eps

Signalfit

We calculated Q from the ring dawn signal.

Displacement sensor

Electrostatic act.

Excite fiber modes

Hea

t lin

ks (A

l 99.

999%

)

Wires (C85)

Cable of act.Sensor

4.Measurement result Requirement (5x106@20K)

6.4x106@20K,88Hz

Fiber 2 High Q

We measured Q values of two kinds of sapphire fiber whose thermal conductivity is higher than the requirement value. One of them (fiber 2) has high Q which is higher than requirement value. This means even non-monolithic fiber can have high Q. HEM quality and thermopolishing might improve Q value.

Modal simulationf1 f2 f3

0.86x106@20K,94Hz

Fiber 1 Low Q

103

104

105

106

107

0 50 100 150 200 250 300Q

T [K]

Impex Monolithic f1 (94Hz)Impex Monolithic f21 (1260Hz)Impex Monolithic f22 (1268Hz)Impex Monolithic f31 (3712Hz)Impex Monolithic f32 (3741Hz)

calc(TED) 94Hzcalc(TED) 1268Hzcalc(TED) 3741Hz

103

104

105

106

107

0 50 100 150 200 250 300

Q

T [K]

Impex Non-Monolithic f1 (88Hz)Impex Non-Monolithic f21(1220Hz)Impex Non-Monolithic f31(3515Hz)

calc(TED) 88Hzcalc(TED) 1224Hzcalc(TED) 3515Hz

Allen Scheie, PA, USDan Chen, Japan

Due giovani “marziani” discesi nel G23 presso Ed. Marconi a La SapienzaHanno portato avanti gl esperimenti,ma c’è ancora del lavoro da fare (Q meas)!

Progetto R&D per Advanced Virgo/ET

test optoelettronico di una scheda per la rivelazione omodinadi radiazione laser in un apparato di squeezing 

Majorana,Puppo,Rapagnani, RicciG23, Marconi

Proposte @G23 AA 2013‐14

SHOTTERMICO  SPECCHI

SISMICONEWTONIANOTERMICO SOSPENSIONI

PRESSIONE RADIAZIONE

RUMORE QUANTISTICO IN UN INTERFEROMETRO MICHELSON 

INTERFEROMETRO: USA LA LUCE LASER  PER MONITORARE LO  

STATO DI MOTO DEGLI SPECCHI  SOSPESI

SHOTRUMORE FASE RADIAZIONE

FLUTTUAZIONE  POSIZIONE SPECCHI

RUMOREPRESSIONERADIAZIONE 

RUMORE AMPIEZZA RADIAZIONE

FLUTTUAZIONE  MOMENTO SPECCHI

PRINCIPIO DI INDETERMINAZIONE

X2

X1

7

RUMORE QUANTISTICO DELL’INTERFEROMETRO 

( ) 12SH O T

in

cL Ph λν

π= h

RPh ν( ) = 1mν 2L

hPin

2π 3λc

( ) ( ) ( )2 2

TOT SHOT RPh h hν ν ν= +

SQLh = h

π 2mL2ν 22

optP cmπ λν=

OTTIMIZZAZIONE  ALLA  FREQUENZA  νRISPETTO ALLA POTENZA     SQL

8

RIVELAZIONE OMODINA

BILANCIAMENTO OTTICO: STESSA POTENZA INCIDENTE SUI DUE FOTODIODI

BILANCIAMENTO ELETTRONICO:  STESSE PRESTAZIONI DELLSTESSE PRESTAZIONI DELL’’ELETTONICA DEI DUE FOTODIODI ELETTONICA DEI DUE FOTODIODI 

STESSE PRESTAZIONI DELLSTESSE PRESTAZIONI DELL’’ELETTONICA DI SOMMA E DIFFERENZA  ELETTONICA DI SOMMA E DIFFERENZA  

BASSO RUMOREBASSO RUMORE:  :  ALMENO 10 VOLTE SOTTO LO SHOT NOISE DEL LOCAL OSCILLATORALMENO 10 VOLTE SOTTO LO SHOT NOISE DEL LOCAL OSCILLATOR

PROTOTIPO DI OMODINA

SELF SUBTRACTION

SOMMA

11

TEST DEL PROTOTIPOMISURA DEL RUMORE ALLE USCITE DEI BLOCCHI  E DELLE FUNZIONI DI TRASFERIMENTO

MISURA DEL RUMORE  DEL LOCAL OSCILLATOR CON AUTO‐OMODINA

COMMON MODE

AMPLIFICATORI A TRANSIMPEDENZA

PROTOTIPO DI OMODINA

13